The present invention relates to a fabric having excellent heat resistance, stability in pleating process, and shape maintenance at high temperatures after pleating.
The fabric of the present invention can be suitably used, for example, as a filter medium for collecting hot dust emitted from refuse incinerators, coal boilers, metal melting furnaces, etc.
As filters for collecting the dust emitted, for example, from refuse incinerators, coal boilers and metal melting furnaces, bag filters have been used, as is well-known.
Bag filter media are required to have heat resistance, since the exhaust gas temperatures are in a high temperature range of 150 to 250xc2x0 C., depending on application. Since a high dust collection efficiency is required in such a temperature atmosphere, the filtration area must be kept as large as possible in a limited space, i.e., in a narrow space.
The conventional filter media used at such high temperatures are made of felt produced by laminating a ground fabric and a web using polyphenylene sulfide (hereinafter called xe2x80x9cPPSxe2x80x9d) fibers, metaaramid fibers, polyimide fibers, fluorine fibers or glass fibers, etc., and entangling the fibers using a needle punch or jet water stream, etc.
However, since the bag filter felt has low filtration efficiency, the filtration area must be enlarged to compensate for low efficiency.
A larger filtration area of felt requires a larger dust collector. As a means for providing a large filtration area in a limited space, it is practiced to pleat nonwoven fabrics in the case of general filter media for building air conditioners, air cleaners, vacuum cleaners, household air conditioners, etc., and nonwoven fabrics enhanced in filtration capacity like this are used as filters. However, since the conventional felt for bag filters is soft, it cannot be pleated.
The present invention is intended to solve the above problem, by providing a fabric having good heat resistance, stability in pleating process and shape maintenance at high temperatures after pleating, as a filter medium used at high temperatures of 150xc2x0 C. to 250xc2x0 C. in refuse incinerators, coal boilers, metal melting furnaces, etc.
The present invention provides a heat resistant fabric in which a nonwoven fabric formed of polyphenylene sulfide fibers is impregnated with a synthetic resin in an amount of 5 to 50 wt % based on the total weight of the nonwoven fabric, wherein the fabric stiffness based on the Gurley method specified in JIS L 1096 is in a range of 3000 to 10000 mgf.
Furthermore, the present invention provides a process for producing such a fabric, comprising at least the following steps:
A. producing a nonwoven fabric comprising polyphenylene sulfide fibers as component fibers by the carding method or spunbond method
B. filling clearances among the component fibers of the nonwoven fabric with a synthetic resin in an amount of 5 to 50 wt % based on the total weight of the nonwoven fabric for impregnation
C. drying the nonwoven fabric impregnated with the resin, and
D. processing the dried nonwoven fabric product to a thickness of 0.3 to 3 mm.